1. Field of Invention
The present invention generally relates to the field of semiconductor integrated circuits (ICs), and more particularly, to a process-invariant temperature detection circuit.
2. Description of Related Art
An integrated circuit (IC) is a miniaturized electronic circuit consisting of a handful to millions of discrete electronic components fabricated on the surface of a thin substrate of semiconductor material. ICs are sometimes classified by the type of transistors used within the circuits. One type of transistor typically used in ICs is the bipolar junction transistor, which is an active semiconductor device formed by two p-n junctions. Another class of ICs are complementary metal-oxide-semiconductor (CMOS) devices. CMOS devices use metal-oxide-semiconductor field-effect transistors (MOSFETs), which are field-effect transistors comprised of a channel of p-type or n-type semiconductor material. An integrated circuit that uses both bipolar junction transistors and CMOS in a single device is known as a BiCMOS device.
A genre of circuits and systems require temperature sensing schemes to convert a temperature into a logic state. This logic state may be used to shut down the system or to raise a logic flag. For example, when a BiCMOS power integrated circuit is in operation, the transistors and other electronic components of the circuit dissipate heat. As the temperature approaches a certain level, the circuit may not operate as efficiently or may not perform as desired. In some situations, the circuit may even be damaged when it reaches a certain temperature. Therefore it is essential for many BiCMOS integrated circuits to include circuitry to detect a specific temperature in order to respond to these over temperature conditions.
Conventional BiCMOS temperature detection circuits are subject to variations in process parameters and considerable effort may be required to integrate the conventional temperature detection circuit into an IC. In addition, the conventional temperature detection circuit cannot be easily ported from one BiCMOS platform to another. When a different BiCMOS process is required, additional design and experimentation must be performed to integrate the temperature detection circuit into the new process.